Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$90.29	3.300%	$93.2696	$93.27	$93.25	$93.30
Purchase #2	$249.46	4.376%	$260.3764	$260.38	$260.40	$260.40
Purchase #3	$178.34	6.713%	$190.312	$190.31	$190.30	$190.30
Purchase #4	$239.67	11.767%	$267.872	$267.87	$267.85	$267.90
Purchase #5	$144.38	5.116%	$151.7665	$151.77	$151.75	$151.80
Purchase #6	$242.61	6.380%	$258.0885	$258.09	$258.10	$258.10
Purchase #7	$96.67	3.175%	$99.7393	$99.74	$99.75	$99.70
7 purchase totals =	$1,241.42		$1,321.4243	$1,321.43	$1,321.40	$1,321.50